The present invention relates to the field of window sash locks.
Burglaries in the United States have been increasing at alarming rates. Typically, a burglar breaks a window pane and actuates the sash latch to enable him to open the window and enter the home. Many homeowners have spent considerable sums on burglar alarm systems which often cost thousands of dollars. These systems are subject to false alarms which can be very annoying to the occupants, neighbors, and to the police. Also, many people cannot afford them.
Another solution to this problem is to bore holes through the upper and lower sash, and insert pins through the holes. Although most people can handle conventional screwdrivers, boring holes is an unsuitable task for many.
One kit on the market instructs the homeowner to use a special wrench to screw the pins through the holes bored by the homeowner. The pins, recessed within the boreholes, then prevent motion of the upper or lower sash to thus deter a burglar. However, each time the occupant wishes to open the windows he must insert the special wrench supplied with the kit into the boreholes and rotate the wrench until the pins are retracted. This is a nuisance, and the wrenches can be lost. Another similar technique is to insert pins through the boreholes until the heads of the pins are flush with lefthand and righthand inside surfaces of the sash. A magnet is applied to the pin heads to retract the pins from the upper sash borehole. Often, the magnets will not work since the boreholes in each sash are not exactly aligned with each other, to produce a resistance force which cannot be overcome by the magnet. The windowsashes must then be "jiggled" until the alignment is corrected to permit the magnet to withdraw the pins, which is a time consuming annoyance. Also, the security of these devices is very limited, as the burglar can obtain the special wrench and the magnet from the same source as the homeowner.
Window sash latches or slidable bolts are also marketed having key actuated locks built therein. Since the screws for maintaining the locks in position are exposed, screws with regular heads are not used, since the burglar can break the window and easily employ an ordinary screwdriver to unscrew the locks. Hence "one way" screw heads are used, and the screws cannot be unscrewed by the user with a screwdriver. If the fixtures are misaligned upon being mounted upon the upper and lower sash during installation by the often inexperienced user, he or she is in trouble since the "one way" screws cannot be removed with a screwdriver for a second "try". However, the "one way" screws can be sheared off with a hammer and chisel or may often be removed by a gripper type wrench, so that these key actuated locks mounted with "one way" screws, still only provide limited real security.
Also, inevitably, at least one of the two keys supplied with these devices get lost. When keys are duplicated, typically several times over the years, they may no longer open the locks due to tolerance variations upon duplication. Also, locks for one set of windows may require different keys than locks for other sets of windows, to cause confusion and annoyance. Additionally, if both keys supplied for each lock are lost, the user will often hire a locksmith to create a new key which costs much more than the initial price of the lock, or may eventually obtain the services of a handy person who would know how to shear off the screw heads or remove them with a gripper wrench. Thus, what is really needed is a high security lock which is installed with ordinary "two way" screws.